The present invention claims the priority under 35 U.S.C. xc2xa7 119 of German Application No. 198 19 526.5 filed Apr. 30, 1998, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The invention relates to a press jacket of a press device, with grooves and/or blind bores provided in the outer circumferential surface, for treating a material web, in particular a paper or cardboard web, in a nip.
2. Discussion of Background Information
Press jackets of this type are used, for example, with press devices where a flexible press jacket that revolves around a rigid support is pressed against, in particular, a rigid opposing surface. A material web, which may be a paper web or a cardboard web, is guided through a nip formed between the flexible press jacket and the opposing surface. Due to the flexibility of the press jacket, it also can be used with other press devices, such as a jacket of a shoe press unit in an extended nip press.
In order to reduce the hydraulic pressure in the nip, as well as to improve drainage, press jackets are partially provided with grooves and/or blind bores that are intended to provide additional water storage volume, which is maintained as constant as possible during operation. The groove width usually lies within a range from 0.5 to 1.5 mm, and the preferred groove width is 1.0 mm. The depth of the parallel side walls of such grooves usually lies within a range from 0.5 to 2.0 mm, and the preferred depth is 1.0 mm. A portion of the grooves may have a conical shape, with an angle of 5xc2x0 to 15xc2x0. A press jacket of this type has been disclosed, for example, by U.S. Pat. No. 5,543,015. Moreover, the blind bores usually have a diameter in the range from 1.6 to 2.8 mm, where the preferred diameter is 2.2 mm. Blind bores of this kind usually have a depth in the range from 1.5 to 2.5 mm, where the preferred depth is 2.0 mm. As a rule, these blind bores are cylindrically formed.
Due to the high degree of stress in the nip, as well as the flow properties of the elastomeric materials that are used for such press jackets, the grooves or blind bores are xe2x80x9cpressed shutxe2x80x9d during operation, such that a cross-sectional reduction takes place, particularly in the opening region of the groove and/or blind bore. Consequently, the available storage volume during operation is considerably reduced in relation to the original storage volume that existed in the new state and in the absence of stress. Hence, the advantage sought with the grooves or the blind bores, of an increased drainage capacity in the nip by means of the additional storage volume, is at least partially nullified. For example, experience during actual use has shown that the grooves of the press jacket disclosed in U.S. Pat. No. 5,543,015, which extend conically at an angle of 5xc2x0 to 15xc2x0, have resulted in practically no improvements during operation, at least thus far.
The present invention provides a press jacket of a press device, with grooves and/or blind bores provided in its outer circumferential surface, for treating a material web in a nip which, despite the relatively high press loads and the flow properties of the elastomeric materials usually used with such press jackets, maintains as large a storage volume as possible during operation.
The present invention provides a press jacket having grooves and/or blind bores, whose side walls in the opening region are provided with a bevel and/or have a rounded section that extends along a curved line, such that the grooves and/or blind bores counteract the above-mentioned volume reduction that occurs when a conventional press is loaded.
According to the present invention, the volume reduction that occurs with each press loading is counteracted because in the critical opening region of each groove or bore, a bevel, or a rounded section that extends along a curved line, is provided which completely or at least partially compensates for the xe2x80x9cpressing shutxe2x80x9d of the grooves or of the blind bores. The form and positioning of the grooves and/or bores disclosed for this purpose relate to a press jacket in its new state.
The edge length of the opening region bevel, measured in the direction of the groove or bore depth, is preferably approximately 1 to 3 times, and preferably approximately 2 times, the edge length measured in the longitudinal direction, perpendicular to the direction of groove or bore depth. In particular, the edge length of the bevel measured in the longitudinal direction may be in the range of approximately 0.1 mm to 0.3 mm, and preferably is approximately 0.2 mm.
Corresponding measurements also may be provided for a rounded opening region section that extends along a curved line. In this instance, these measurements relate to a tangent resting against the rounded section.
For instance, according to an embodiment of the invention, the edge length of the rounded sectionxe2x80x94measured in the direction of the groove or bore depth, preferably with reference to a tangent resting against the rounded sectionxe2x80x94is approximately 1 to 3 times, and preferably is approximately 2 times, the edge length measured in the longitudinal direction, again with reference to the tangent. Further, the edge length of the rounded sectionxe2x80x94measured in the longitudinal direction, preferably with reference to the tangent resting against the rounded sectionxe2x80x94can lie within a range from approximately 0.1 mm to approximately 0.3 mm, and preferably is approximately 0.2 mm.
The edge length of the bevel or the rounded section, measured in the direction of the groove or bore depth, may be formed such that a cylindrical wall section remains positioned between the bottom of the respective groove or blind bore, and the bevel or rounded section.
The rounded section can extend along a curved line that corresponds, or at least essentially corresponds, to an arc or to an involuted curve.
According to another press jacket embodiment of the invention, the bevel or the rounded section is disposed immediately adjacent the outer edge of the respective groove or blind bore.
According to yet another embodiment, the bevel or rounded section is offset inwardly, and at a specific distance, from to the outer edge of the respective groove or blind bore, in the direction of the groove or bore depth.
In the case of a groove in the press jacket, preferably at least the side walls of the groove that extend in the circumference direction of the press jacket are provided with a bevel or rounded section.
The side wall of each blind bore is preferably provided with an annular bevel, or a rounded section, that extends over the entire inner circumference.
The present invention provides a press jacket for a press device for treating a material web in a nip which includes an outer circumferential surface, where the outer circumferential surface includes a groove or a blind bore, where the groove blind bore has a side wall in an opening region, and where the side wall has a bevel or a rounded section that extends along a curved line, such that the bevel and rounded section counteracts a reduction in volume in the groove or blind bore when the press device is loaded. The material web may be a paper web or a cardboard web. Further, a depth edge length of the bevel measured in the direction of groove or bore depth may be approximately 1 to 3 times a longitudinal edge length measured in a longitudinal direction. The depth edge length preferably is approximately 2 times the longitudinal edge length. Further, a longitudinal edge length of the bevel measured in the longitudinal direction may be between approximately 0.1 mm and approximately 0.3 mm, and preferably is approximately 0.2 mm.
According to another aspect of the present invention, a depth edge length of the rounded section measured in the direction of the groove or bore depth may be approximately 1 to 3 times a longitudinal edge length measured in a longitudinal direction, and preferably is approximately 2 times the longitudinal edge length. The depth edge length and the longitudinal edge length may be determined with reference to a tangent that rests against the rounded section. Moreover, a longitudinal edge length of the rounded section measured in a longitudinal direction may be between approximately 0.1 mm and approximately 0.3 mm, and preferably is approximately 0.2 mm. The longitudinal edge length may be determined with reference to a tangent that rests against the rounded section.
According to yet another aspect of the invention, the press jacket may include a cylindrical wall section that is disposed between the bevel or the rounded section, and the bottom of the groove or the blind bore. The side wall""s rounded section may extend along a curved line that substantially corresponds to an arc. Alternatively, the rounded section may extend along a curved line that substantially corresponds to an involuted curve.
The groove or blind bore of the press jacket of the present invention may have an outer edge, and the bevel or the rounded section may be positioned on the outer edge. The bevel or the rounded section may be positioned offset in the direction of groove or bore depth, and at a distance, from the outer edge. Moreover, the side wall of the groove may extend in a circumferential direction of the press jacket, and the side wall may include the bevel or the rounded section. Alternatively, the side wall of the blind bore may include the bevel or the rounded section, and the bevel or the rounded section may extend over the entire inner circumferential surface of the side wall. Further, the bevel may be an annular bevel. Moreover, the press device may be a shoe press unit, and the nip may be an extended nip.
The present invention also includes a method for improving the drainage of water from a material web by: providing a flexible press jacket, forming a nip between the flexible press jacket and a rigid opposing surface, transporting the web through the nip, and applying a press load to the web in the nip, where the flexible press jacket includes an outer circumferential surface, where the outer circumferential surface includes a groove or a blind bore having a side wall in an opening region, and where the side wall has a bevel or a rounded section that extends along a curved line. The material web may be a paper web or a cardboard web. Moreover, a depth edge length of the bevel measured in the direction of the groove or bore depth may be approximately 1 to 3 times, and preferably is 2 times, a longitudinal edge length measured in a longitudinal direction. Further, a longitudinal edge length of the bevel measured in a longitudinal direction may be between approximately 0.1 mm and approximately 0.3 mm.
According to another aspect of the present inventive method, a depth edge length of the rounded section, measured in a direction of the groove or bore depth, may be approximately 1 to 3 times a longitudinal edge length measured in a longitudinal direction. Preferably, the depth edge length and the longitudinal edge length are determined with reference to a tangent that rests against the rounded section. Moreover, a longitudinal edge length of the rounded section measured in a longitudinal direction may be between approximately 0.1 mm and approximately 0.3 mm. The longitudinal edge length preferably is determined with reference to a tangent that rests against the rounded section.
According to yet another aspect of the invention, the press jacket may include a cylindrical wall section disposed between the bevel or the rounded section, and the bottom of the groove or the blind bore. The rounded section may extend along a curved line that substantially corresponds to an arc. Alternatively, the rounded section extends along a curved line that substantially corresponds to an involuted curve. Moreover, the groove or the blind bore may have an outer edge, and the bevel or the rounded section may be positioned on the outer edge. Further, the bevel or the rounded section may be positioned offset in a direction of the groove or the bore depth, and at a distance from the outer edge. The side wall of the groove may extend in a circumferential direction of the press jacket, and the side wall may include the bevel or the rounded section. Similarly, the side wall of the blind bore may include the bevel or the rounded section, and the bevel or the rounded section may extend over an entire inner circumferential surface of the side wall. Further, according to the improved method for draining a web, the press device may be a shoe press unit, and the nip may be an extended nip.
Further, the aforementioned and following characteristic features of the present invention can be used not only in the described combinations, but also in other combinations or alone, without departing from the scope of the invention. Further embodiments and advantages can be seen from the detailed description and the accompanying Figures.